The etiology of eruptive vellus hair cysts (EVHCs) is not well understood.1 Vellus hair is thin, short, lightly colored hair that normally grows on the face, trunk, and limbs. During puberty, vellus hair changes to terminal hair, which is darker, longer, and thicker, on certain parts of the body, including the scalp, face, axilla, and pubic area.2
Some have hypothesized that EVHC is caused by a developmental abnormality of the vellus hair follicle that leads to follicular occlusion, cystic dilatation, and retention of keratin. Others postulate EVHC to be a benign follicular hamartoma.1 A minority of EVHC cases appear to be inherited in an autosomal dominant fashion,3 which may be the case in this patient given similar findings in his father.
Eruptive vellus hair cysts typically appear as 1-mm to 3-mm monomorphic, hyperpigmented papules occurring most commonly on the chest, but may also present elsewhere on the body. The lesions range in color from skin-colored, brown, red, green, pink, yellow, black, gray, to blue. The papules are usually smooth and dome shaped, although crusting or umbilication is occasionally observed. The cysts usually are asymptomatic and are rarely painful or pruritic.1,3-6
The epidemiology of EVHC is not well characterized because it is an uncommon disorder.3 More than 220 cases have been reported in the literature.1 These cysts most commonly present during the first 3 decades of life, and in females more than males. All races may be affected, but the literature suggests a predominance in whites.3
Eruptive vellus hair cysts may be confused with acne, milia, Molluscum contagiosum, syringomas, folliculitis, keratosis pilaris, and steatocystoma multiplex. The diagnosis of EVHC is often made based on the history and physical examination. Definitive diagnosis is established by histopathology, which shows follicular cysts lined by stratified squamous epithelium and filled with laminated keratin and vellus hair.1,3-5 An alternative diagnostic technique to biopsy is to incise or puncture the cyst and look for vellus hairs under microscopy.6
Treatment usually is not necessary given the benign nature of the condition. Approximately 25% of cases may resolve spontaneously over months to years via transepidermal elimination.1 However, in symptomatic cases or for patients strongly desiring treatment, several therapies exist.
Keratolytic creams containing tretinoin, tazarotene, salicylic acid, or urea may be helpful. Incision with small needles or blades followed by gentle curettage and electrodessication can remove lesions with minimal risk of scarring. Cryotherapy and laser also can be tried but have a higher risk of scarring and dyspigmentation.1,3,6
The family was educated regarding the benign nature of EVHC. Given that the boy’s lesions were asymptomatic, like his father’s, and not otherwise bothersome, monitoring without treatment was recommended.
1. Zaharia D, Kanitakis J. Eruptive vellus hair cysts: report of a new case with immunohistochemical study and literature review. Dermatology. 2012;224(1):15-19.
2. Marks Jr JG, Miller JJ. Structure and function of the skin. In: Lookingbill and Marks’ Principles of Dermatology. 5th ed. Elsevier Saunders; 2013:2-10.
3. Torchia D, Vega J, Schachner LA. Eruptive vellus hair cysts: a systematic review. Am J Clin Dermatol. 2012;13(1):19-28.
4. Emer J, Pan M, Bernardo S, Sidhu H. A young boy with itchy papules on the trunk. J Clin Aesthet Dermatol. 2013;6(4):43-45.
5. Patel U, Terushkin V, Fischer M, Kamino H, Patel R. Eruptive vellus hair cysts. Dermatol Online J. 2012;18(12):7.
6. Paller AS, Mancini AJ. Disorders of hair and nails. In: Hurwitz Clinical Pediatric Dermatology: A Textbook of Skin Disorders of Childhood and Adolescence. 5th ed. Elsevier; 2016:136-174.